Your online aloe encyclopedia
Botanical Name: Aloe species
Common Name(s): Aloe
Categories: Aloes and Succulents, Shrubs and Perennials
The Aloe genus is restricted to Africa and Madagascar, and many species are indigenous to South Africa. Aloes occur in a wide range of climates, so the variance in the species is huge, from tree-like aloes, such as A. barbarae, to the clump forming A. arborescens, rosette forming A. maculata and tiny A. parvula. Flower colours range from white to shades of yellow, orange, red and pink. Most aloes are drought tolerant, making them a good choice for waterwise gardens. Aloes produce copious amounts of pollen and nectar, attracting birds and insects when they are in flower. Many aloe hybrids have been cultivated to suit garden conditions.
Botanical Pronunciation: AL-oh
With their usually spiny leaves arranged in neat rosettes, and tall candle-like inflorescences in predominantly red and vibrant orange hues, aloes are increasingly sought after by gardeners and horticulturists, as they brighten up the dull winter landscape.
Aloes come in a variety of growth forms, from small miniatures to tall single-stemmed or branched trees, while certain species even form large, tangled shrubs. The usually swollen and succulent leaves are more or less lance- or sword-shaped in outline and boat-shaped in cross-section. Leaves are arranged in terminal clusters (rosettes) and are armed along their margins with usually sharp, but sometimes soft, teeth.
Flowers are grouped in candle-like or cone-shaped inflorescences, which can be branched or simple. The most common shape of flowers found in Aloe is tubular flowers, although some species have curved or even bell-shaped flowers.
Flowers are typically brightly coloured and most often in various hues of red, orange and yellow, but there are also some species with green, pink or white flowers. The vast majority of aloes flower in winter, while some groups, like the grass aloes for instance, usually flower in spring or summer.
Aloe fruit are capsules that dry out and split open to release the mature small, brown to black, angled seeds that sometimes have a narrow or prominent translucent or white wing. The wing is thought to aid wind dispersal of the seeds. There are a group of ± 20 aloes from Madagascar and the Mascarene islands that have a fleshy berry, which does not dry out completely and become woody. These berried aloes are sometimes separated into the genus Lomatophyllum Willd. and their leaves are generally not as succulent as those of other aloes.
Aloes are mostly long-lived plants, especially the larger species. A specific quiver tree (Aloidendron dichotomum) was estimated to be between 100-145 years old, while some exceptionally tall specimens (of over 10 m) of Aloe marlothii may even be over 200 years old.
All species of Aloe (except for A. vera L.) appear on CITES (Convention on the International Trade in Endangered Species of Wild Fauna and Flora) Appendices, meaning that trade in aloes is controlled to prevent utilisation that would be incompatible with their survival. A total of 21 species, including varieties of some of these species, are included in Appendix I and trade in specimens of these species is permitted only in exceptional circumstances. The other aloes are all on Appendix II and therefore certain permits are required to trade in these aloes.
In South Africa most aloes are also protected, with very few exceptions, by environmental legislation in all nine provinces. It is thus illegal to remove plants from their natural habitat without the necessary collecting and transport permits issued by a provincial or other nature conservation authority, and consent from the land owner.
In the latest Red List of South African Plants, a total of 46 aloes are listed as species of conservation concern: Critically Endangered: 5; Endangered: 4; Vulnerable: 15; Near-threatened: 10; Rare: 9; Declining: 1; Data Deficient –Insignificantly known: 2.
Common threats listed for the survival of these aloes are restricted distribution ranges, habitat destruction and fragmentation, collecting for horticultural purposes, invasive alien encroachment, and harvesting for medicinal purposes.
Distribution and Habitat
Aloes are prominent components of many, mainly arid, African landscapes. There are currently ±600 different aloes recognised. Members of the genus can be found in Africa (±405), the Arabian Peninsula (±45), Socotra (4), Madagascar (±145) and the Mascarene and other Western Indian Ocean Islands (±7).
On the African continent aloes occur over much of Sub-Saharan Africa, although they are mainly concentrated in the southern and eastern regions of the continent; only two or three aloes are found in western Africa. High centres of aloe diversity are found in South Africa (±155), Madagascar (±145), Tropical East Africa (i.e. Kenya, Tanzania and Uganda; ±85), the Horn of Africa region (i.e. Ethiopia, Eritrea and Somalia; ±76) and the Arabian Peninsula (±45).
In South Africa the ±155 species of aloe can be found in almost all vegetation types, from the arid to semi-arid regions of the Karoo, the winter rainfall fynbos region, succulent thickets, grassland and savanna, and even in comparatively high-rainfall forests. Most aloes have small or fairly limited distribution ranges, and are often associated with only one of these vegetation regions, but a few are widespread, like Aloe arborescens and Aloe maculata.